1. Field of the Invention
This invention pertains to fluid control valves used to dispense a fluid wherein the valve contains means for coupling a sensor to the valve for detection and monitoring of fluid flow and fluid pressure inside the valve housing or manifold sleeve. Valves of this type are suited for use in dispensing a first or control fluid which is mixed with a second fluid or mixture of fluids. Fluid flow through or fluid pressure inside the valve housing (manifold sleeve) can be detected and used to activate the flow of the second fluid or fluids unless the first fluid is flowing at a desired pressure level through the control valve. Conversely, lack of flow or pressure inside the valve housing or manifold sleeve can be detected and used to deactivate the second control valve(s).
Valves, according to the present invention, are ideally suited for dispensing oxygen in an anesthesia machine for delivering a gas mixture of oxygen and a gaseous anesthetic agent to a patient undergoing surgery. In order to provide maximum patient safety, conventional anesthesia machines are equipped with cooperating valves so that if the oxygen flow (pressure) in the patient circuit falls below a given level, all other valves are deactivated thus stopping flow of the gaseous anesthetic agent to the patient. It is well-known that unless at least 20% of the gas mixture is oxygen, the mixture becomes highly toxic and lethal to the patient. Oxygen is required to sustain life while the patient is in a state of anesthesia.
2. Description of the Prior Art
In most conventional anesthesia machines, to provide patient safety, pressure activated check valves are provided in the anesthetic agent dispensing lines which are coupled to the oxygen delivery lines. In those systems where was no control mechanism which would relate oxygen delivered to the patient to activation or deactivation of the anesthetic agent control valves. Thus, if the anesthesiologist accidentally turned off the oxygen valve, it was possible to deliver a lethal dose of anesthetic to a patient undergoing surgery.
One solution to minimizing the risk of allowing toxic or lethal quantities of anesthetic to be delivered to a patient is shown in the article by Scurlock, published in volume 42 of Anesthesiology, No. 2, (February, 1975). In that reference, the author discloses the use of a fluidic device employing an OR/NOR logic gate for controlling pressure activated electric switches in an anesthesia machine. When the oxygen pressure or oxygen flow rate drops below a safe level, the pressure activated electric switches would close the anesthesia lines and an alarm would sound.